Rate measuring and comparing circuit



Nov. 6, 1951 A. M. GRASS 2,573,840

RATE MEASURING AND COMPARING QIRCUIT Filed oct. 1o, 1945 2 SHEETS-SHEET 1 Nov. 6, 1951 A. M. GRASS RATE MEASURING AND COMPARING CIRCUIT 2 SHEETS- SHEET 2 Filed Oct. 10, 1945 FIG. .2v

54m/5e 52 FIGSB l nf H^74 y lNysNToR ALBERT M; GRASS ATTORNEY Patented Nov. 6, 1.951

RATE MEASURING AND COBIPARING CIRCUIT Albert M. Grass, Quincy, Mass., assignor, by mesne assignments, to the United States of America as represented Navy by the Secretary of the Application October 10, 1945, Serial No. 621,576

14 Claims. 1 kThis invention relates to measurement systems, more particularly automatic tracking systems, and especially such systems employed with pulse echo radio apparatus.

The primary object o'f the invention is to generally improve measurement systems of the character speciiied.

A more particular object is to provide a measur ment'v system suitable for automatic tracking di range, although the system is lalso useable for automatictracking of angle.

VVVAnother object ofV the invention is to devise such a system including means for slewing the controls under motor drive at any desired rate.

@Still another. object of the invention is to providev means for not only measuring the desired quantity (for example, range), but also for measity memory, but also a ready change of the remembered velocity. Y i

@Still ,another objectY of the invention is to provide motion v.for two output shafts; one for the measurement, and the other for the measurement rate, said output shafts being suitable for connection to a standard computer forre control of weapons.

YTo accomplish the foregoing general objects, andother more speciiic objects .which will hereinafter appear, my invention resides in the circuit Y elements and their relation one to the other as'v Fig; 1A is a schematic representation of four Y switches forming a part of the apparatus shown in IFig. 1;

Fig. 2 represents in idealized fashion the dis` ,play on an A. type scope, and is explanatory of the invention;

Fig. .v3 'shows a. seriesV of related voltage-time curves explanatory of the invention; and,

2 Fig. 4 is a simplied drawing of a differential gear forming a part of the apparatus shown in Fig. 1.

Referring now to the drawing, and more particularly to Fig. l, the apparatus in brief sum-v mary comprises a, reversible motor I2 responsive to a position error voltage supplied at I4. The motor I2 drives a measurement potentiometer I8, which varies a measurement potential at lead I8, in that direction which will reduce the error voltage at I4 to zero, thus bringing the motor I2 to rest. Motor I2 also drives an electrical generator 20 which generates a potential which is linearly proportional to the rate ci' change of the measurement. The measurement-rate potential from generator 20 is supplied to a second reversible motor 22, which motor in turn drives a measurement-rate potentiometer 24. The potential from potentiometer 24 is employed in opposition to the potential from generator 20, thus bringing the motor 22 and the potentiometer 24 to a position proportional to the rate of change of the measurement.

The specic apparatus here disclosed has been designed for range tracking in connection with radio pulse echo (radar)` systems. It is equally applicable to angle tracking, and to the tracking of other variable measurements, but for convenience the description will be in terms of range tracking. The apparatus is intended not only for automatic tracking, but also includes slewing means, and aided tracking means. Itwill be seen that if switch 2B is changed from its upper position to its lower position, the error voltage from source I4 will be replaced by a substitute voltage from a slew potentiometer 28. This will cause the motor I2 to work continuously at a constant speed, the speed being determined by adjustment of the slew potentiometer 28. At the same time a switch 30 may be moved from its upper to its lower position, thereby grounding the f range rate circuit, for a range rate indication anyway would be without significance during slewing.

For aided tracking a switch 32 is moved from its upper to its lower position, thereby removing the source of error voltage and making the motor I2 wholly inoperative. At the same time a magnetic clutch 34, which was previously released, is now energized through switch '34',

thereby connecting the'motor 22 instead of the motor I2 to the range potentiometer I6. Also another magnetic clutch 36, which previously was energized through switch 36', is now de-energized, thereby disconnecting the motor,` 22.,

lother depending on the phase of the alternating current.

The drive from motor l2 to the range potentiometer I6 is schematically indicated by bevel gearing 82 and 84 and screw 86.

The generator 20 is a permanent magnet eld D. C. tachometer the output of which is supplied thru lead 88, switch 30, and a lter 90, to the amplier 44. The output of D. C. tachometer 20 is also applied across a voltage divider 92, so that a4 desired fraction of the voltage may be led through wire 94 back to amplifier 42. The degenerative feed back system is considered important not only to stabilize the system and avoid hunting, but also because it permits the operation of motor I2 to be made substantially linear.

The amplifier 44 is also preferably a bridge modulator amplifier of the type disclosed in my aforesaid co-pending application, Serial No. 596,725, and is supplied with alternating current from a standard source 80. The phase of this alternating current is shifted 90, and its amplitude is controlled by the D. C. potential supplied across leads a and 0. The phase of the alternating current is shifted from to 180 upon reversal in sign of the D. C. potential across leads (la), ((0.2,

YThe motor 22 is a two-phase induction motor. One field coil is supplied from the standard alternating current source 80, and the other fleldcoil isv energized by the output from amplifier 44.

'It will be noted that the range rate potential is applied to point b at one end of a voltage divider 96 while the output of the permanent magnet eld D. C. tachometer 46 is connected to the other end of the voltage divider 96. The voltage supplied to the amplifier at a depends on the adjustment of the range rate potentiometer 24, and is fed in opposition to the range rate potential supplied at point 1). When the potential at points a and c are equal, the motor 2,2 comes to rest, together with the tachometer 46 and the range rate potentiometer 24. The potential at a is then equal to the potential at 12, since there is no tachometer output potential, and this isthe desired balance which would indicate that the range rate is constant.

Inasmuch as the apparatus is ordinarily used4 with a computer for gun fire control, a range output shaft |00 may be provided, geared to potentiometer I6 atK| |12 and a range rate output shaft |04 may be provided, geared to range rate potentiometer 24 at |66. A range dial |08 andra range rate dial lll! may also be gearedl to the other shafts, as is schematically indicated on the drawing. y

The nature of the diierential gear indicated at 40 in Fig. 1 is better shown in Fig. 4. Bevel gear ||2 is connected through spur gears ||4 and |I6 to shaft II8, while bevel gear is connected thru spur gears |22 and |24 to shaftA |26. One or more planet gears |28 are disposed on a spider connected to a shaft |30 passing concentrically through bevel gear |28 and spur gear |22. The shafts H8, |26 and |38 correspond to the similarly numbered shafts shown in Fig. 1. It will be evident that motion of either shaft ||8 or |26 Will be applied to shaft |30. Thus in the aided tracking position, motor 22 will turn shaft |38, and handle 38 will additionally control shaft |30. At this time any rotation of gear |32 by gear |34 is without significance because the magnetic clutch 36 is open.

However, during automatic tracking the mag-1 netc clutch 34 isropen, and any rotationof shaft ||8 would cause rotation of shaft |26 if shaft |30 were locked. In lieu of this, however, a more direct drive takes place through gear |32 and |34 because at this time the magnetic clutch 36 is energized. The control handle 38 may at the same time be shifted inward to the dotted position shown, thereby disengaging a clutch |36 between the'control handle and the gear |34, so

that the handle need not spin during automatic tracking. It will be understood that the apparatus'inFig. 1 has been simplified for ease in understanding the same, and that in actual practice the switches 3| and 32, and the switches 34' and 36', respectively, for the power supply circuits for the magnetic clutches 34 and 36 may be interconnected as shown in Fig. 1A. Such an arrangement may be employed to switch from automatic to aided tracking. Alternatively, switches 26 and 30 and the axial movement of the control handle 38, may also beappropriately interconnected with the switches shown in Fig. 1A so that movement of a Single master control maybe used to change the apparatus to any,

one of the three operating conditions, that is,` automatic tracking, slewing, and aided tracking.

During aided tracking the motor I2 and tachometer 20 are intentionally driven, by means of the gears 82 and 84, in order to avoid inertia or switching transients both mechanical and electrical which would arise when seeking to start such a mechanical system in motion from rest. This continuous mechanical drive makes it possible to switch directly from, aided tracking to automatic tracking, even at high tracking rates. The output of tachometer 46 is greater than that of tachometer 28, gear ratiosl and other constants in the system being such that the effect of tachometer 46 is the primary control during aided tracking.

It may be well to summarize the diierent switch positions. Switch 32 is placed in the upper position for automatic' tracking and for slewing, and is placed in the lower position for aided tracking. Switch 28 is placed in the upper yposition for automatic tracking and for aided tracking, and is placed in the-lower position' for slewing. Switch 36 is placed in the upper position for automatic tracking and for aided tracking, and in the lower position for slewing.

Switch 3| is closed for automatic tracking and Y for slewing, and is opened for aided tracking (to avoid wasteful loss of energy in turning the range servo). The switch (not shown) for energizingl the magnetic clutch 34 is opened for automatic tracking and for slewing, and is closed for aided tracking;` The switch (not shown) for magnetic clutch 36 is closed for automatic tracking and for target followed by the manual control handle.

This not only follows the target, but sets up an approximately correct range rate on the range rate potentiometer. yBy then shifting the apparatus to automatic tracking, the marker will In practice it is usually possible to switch directly from the slewing condition to the automatic tracking conf follow the target automatically.

dition, without going fthroughtheeaided'traoking operation. Thisisf'sobecause the maximum speed at which the automatic trackingfmechanismwll lock fon the :target greatly exceedsthefminimuml slewing speed. When the '.systemis `automatically vtracking Vit :may run rinto `itrouble by engaging a series of L.echoes other -than'1the one sought to be tracked, .thusmaking it impossiiile to :automatically .track the target, .and at such time the apparatus ymay be shifted to the laided tracking condition, whereupon fthe marker Vvwill automatically coast a-t the .previous range-rate. If the observer sees .that 4this coasting -is not adequate lto follow the target, he'may crank in a :correction by means .of the manual control handle. Although the operator merely yloper-- ates'the handle in .such vaf-marmer as to keep the imarker on the ftarget, during this operation the range rate potentiometer is :continuously 2being Y-reset :until the correct rate 4iis established. When the 'target pip moves Vto Va clear =reg-ion where it .can .be .automatically tracked, fthe' apparatus' can againzbe put in the automatic ftracking condition, :and the range .Igatesw'ill againlock on the target.

It will be understood that wh'ilel have shown and described my invention ina preferredftorm, many .changes .may be .made in the circuit fand structure shown, vWithout. departing from the spirit of the invention, as sought to=`be-dened responsive toa ypositionerror voltage, a measurement potentiometer .fdrivenf-by said motor 'to pro-V vide a measurement potential for shifting a measurement indication in that :direction which will reduce the .error voltage :to zzero, a generator driven by said motor to provide a measurement rate potential, va, second reversible motor responsive to the measurement 4rate potential, and a lmeasurement'rate :potentiometer -drivenby said second motor for supplying a potential in opposition to the Imeasurement rate potential.

2. Apparatus Acomprising a-reversible motor freponsive vto a position error voltage,a measurement .potentiometer driven by said motor to-provide a measurement vpotential for shifting -a measurement rindication in that I"direction which willlreduce the -error voltage lto zero, a generator drivenby :said `motor toprovide -a measurement .rate potential, a second `reversible'motor responsive to the @measurement Arate potential, `ai

measurementindication in that vdirection which will reduce the error voltage to zero, 'a generator driven by lsaid :motor `to provide a measurement rate potential, a secondreversible motorfresponsive to the measurement -rate potential, a measurement `rate potentiometer ldriven Eby said second-motor for supplying a potentialin V`opposition to the-measurement rate Vpotential, switch means fonde-energizing said *rst.-reversible unotor, rst clutch dmeans l"for yiiiscennecting Vsaid" t Y measurement rate 'potentiometer -I-romsaidfsec- 75 Efor fslting 'va-measurement indication .nJthBt-.i

ondmotonaseeondmlutch means-.for -.mechanic-:tiny` couplingsaid second motor to said measurement potentiometer whereby said apparatus lmaybe employed for aided tracking, .and a manual :con-"1 trol handle connected to -the measurement-'pow tentiome'ter fand the :measurement Arate :potentiometerzfor Yuse during :aided tracking;

4.Apparatuscomprising a, reversible motor-rfc'-V s'ponsive 'to a, Iposition error voltage, afmeas--V urement potentiometer drivenby said motorfto provide a `fmeasurem'ent Vpotential for* shifting a measurement indication A'in that 'direction 'which Will reduce 'the Aerror voltage to zero, a 'genera-M tor-driven 'by said motor to provide-ameasure-v ment rate potential, `a second reversible motor responsive tothe measurement vrate potentiaL afmeasuremen't rate .potentiometer drfi'ven '-byisad second motor 'ffor'rsupplying a potential lin opposition fto Lthe measurement rate potential, aslewf potentiometer, switch V-mean's for disconnecting switch means for -`(ie-energizing said Aiirs't motor, rst clutch means for disconnecting saidfmeasurement ratepotentiometerfrom -said secondmotor, vand second -clutch Ymeans vfor -mec'hanicaly I Y coupling ysaid second motor to said measurement potentiometer, anda manual control 'handle -connected 1to the measurement Vpotention'ieter and the measurement rate potentiometer "for useduring -aided tracking.

5. Apparatus comprising a kreversible motor' responsive to a yposi-tion error voltage, Va measmeans permitting said apparatus to Lbe employed for slewing, said means comprising, a fslew 'potentometer, 'iirst switch `means for -disconnect- Aing said first motor :from said error "voltage-1 source andconnecting it toY ksaid slew potentiometer, and V-second :switch Imeans Yfor discern-"- necting said second motor from said *measure-"i ment vrate potential', means Ypermitting said 'apparatus to be employed -vfor laided tracking, saidV last-mentioned means comprising, third fswitoh" means :for ,'deenergizing ,said `rst motor, ffiist` clutch means for disconnecting v'said measurement rate potentiometer 'from saidsecondnrotor "andsecond clutch means for mechanically fcoupling said second motor -to said measurement potentiometer, 'a manual. Icontrol :handle #connected :to the lmeasurement potentiometer fanfd the measurement V'rate potentiometerV lfor. use Y"during aided tracking, and means -'to lstabilize the Y operation of therst and lsecond motors.

6. Apparatus comprising a bridge modulator amplifier supplied with a position error voltage" for vcontrolling the 4amplitude and phase of A. '-C., -a two phase motor 'having one eld suppliedVr with the output vof the lbridge modulator ample'- er Iand the vother field supplied with reference`-- A. C., a measurement potentiometer driven by saidmotor Ito provide a measurement potenthl '.19 direction which will vreduce the error 'voltage to zero, avDQC. tachometer driven by' said motor to provide 'a measurement rate potential, al second bridge modulator amplifier supplied with said measurementy rate potential for controlling the amplitude andtphase of A. C V., a second two phase motor having oneield coil supplied with the output ofSaid'bridge modulator amplifier and a second field coil supplied with reference A. C., and a measurement rate potentiometer driven by said second motor for supplying a potential in opposition to the measurement rate potential.

7. Apparatus comprising a bridge modulator amplifier suppliedwith a position error voltage for controlling the `amplitude and phase of A. C., a two phase motor having one field supplied with the output of the bridge modulator amplifier and the other eld supplied with reference A. vC., a measurement potentiometer driven byv said motor to provide a. measurement potential for shifting a measurement indication inthat direction which will reducethe` error voltage to zero, a D. C. tachometer driven by'said motor to provide a measurement rate potential, a second bridge modulator amplifier supplied with said measurement rate potential for controlling the amplitude and phase of A. C., a second two phase motor having one field coil supplied with the output of said bridger modulator amplifier and a second eld coil supplied with reference A. C., a, measurement rate potentiometer driven by said second motor for supplying a potential in oppositionto the measurement rate potential, a slew potentiometer, switchV means for disconnecting the rst bridge modulator amplifier from the error voltageV source and connecting it to said slew potentiometer-when the apparatus is t'obe used for slewing, means adapting said apparatus for aided tracking, said last-mentioned means comprising, switch means for de-energizing said rst motor, rst clutch means for disconnecting said measurement rate potentiometer from said second motor and second clutch means for mechanically' coupling 'saidsecond motor to said measurement potentiometer, and a manual con.

trol handle connected to the measurement potentiometer and the measurement rate potentiom- `eter for use during aided tracking.

8. Apparatus comprising a reversible motor reponsive to a position error voltage, a measurement potentiometer driven by said motor to pro- 'vide a measurement potential for shifting a measurement indication in that direction which will reduce the error voltage to zero, a D. C. tachometer driven by said motor to provide a measurement rate potential, a second motor responsive to said measurement rate potential, a measurement rate potentiometer driven by said second motor for supplying a potential in opposition to the measurement rate potential, means for degeneratively feeding a part of the D. C. tachometer output to stabilize the operation of the first motor, a second D. C. tachometer driven by the second motor, and means to feed a, portion of the second tachometer output in such a direction as to stabilize the operation of the second motor.

9. Apparatus comprising a reversible motor responsive to a position error voltage, a measurement potentiometer driven by said motor to provide a measurement potential for shifting a. measurement indication in that direction which will reduce the error voltage to zero, a D. C. tachometer driven by said motor to provide a measurement rate potential, a second motor responsive 10 .A to said measurement rate potential, a measurei ment'rate potentiometer driven by said"second motor for supplying a potential in opposition'tol the measurement rate potential, a slew poten-f' tiometer, switch means for disconnecting the rst motor from the error voltage source and 'con'- necting it` to saidslew'potentiometer when the apparatusr is to be used for slewing, means adapting said apparatus Afor aided tracking, said lastmentioned means comprising, switchmeans for cle-energizing said first motor, first clutch means for disconnecting said measurement rate poten'- tiometer from said second motor' andl second clutch means for mechanically coupling said second motor to said measurement potentiometer, a manual control handle connectedto the mealsirement potentiometer and the measurementl rate :potentiometer for use during 'aided track-j ing, means for degeneratively 'feeding a partof the D. C. tachometer output to stabilize the operation of the first motor, a second D. C. tachometer driven by the `second motorfa'nd meansjto feedUa portion of the second tachometer output in such a direction as to stabilize the operation of the second motor.

l0. Apparatus comprising a bridge modulator amplifier supplied withA a position error voltage for controlling the amplitude and phase of A. C., a two phase motor having one field supplied with the output of the bridge' modulator/'amplifier and the other eld suppliedwith reference4 A.C. a measurement potentiometer'driven by said mo= tor to provide a measurement potential for shift'- ing a`measurement indication in that directionl which will reduce the error voltage to zero, a D. C. tachometer driven by said motor to provide a measurement rate potential, a second bridge modulator amplier 'supplied' with.' said measurement rate potential forvcontrolling 'the' amplitude and phase of A. C., a second two 'phase motor having one field coil suppliedwithA the output of said bridge modulator amplier and al second field coil supplied with reference A'. C., a measurement rate potentiometer driven'by said second motor for supplying a potential in opposition to the measurement rate potential, means for degeneratively feeding a part of the D. C. tachometer output to the rst bridge modulator amplifier to stabilize the operation of the rst motor, a second D. C. tachometer driven by the second motor, and means to degeneratively feed a portion of the tachometer output to the second bridge modulator amplifier to stabilize the operation of the second mtor.

1l. Apparatus comprising a bridge modulator ampliiier supplied with a position error voltage for controlling the amplitude and phase of A. C., a two phase motor having one field supplied with the output of the bridge modulator amplifier and the other field supplied with reference A. C., a measurement potentiometer driven by said motor to provide a measurement potential for shifting a, measurement indication in that direction which will reduce the error voltage to zero, a D. C. tachometer driven by said motor to provide a measurement rate potential, a second bridge modulator amplifier supplied with said measurement rate potential for controlling the amplitude and phase of A. C., a second two phase motor having one field coil supplied with the output of said bridge modulator amplifier and a second field coil supplied with reference A. C., a measurement rate potentiometer driven by said second motor for supplying a potential in opposition to the measurement rate potential, a slew ateniese Il' potentiometer, switch means, for disconnecting the. .first bridge modulator( amplier fromtne crrorvoltage source and connecting it to.l said slewV potentiometer when the apnaratiisistev be usedafor slewing,` means.. adapting, said apparatus. .fm1 aided tracking. said lastfmentioned. means comprisingv switch means. for de-energzing said lrstrmotor, rst. clutchmeans for disconnecting said'. measurement. rate- .potentiometer from said second. motor and second. clutch meansfor me.- clianically coupling. said second. motor to said measurement potentiometer,` a4 manual control handle connected to the measurement. potenticlmetel:` andthe. measurement rate potentiomf eteriorluse. during. aided tracking, means for degeneratively feeding. a` part. of the D.A C. 'cachemeter1 output to the first bridge modulai-,orl amplinel'. to stabilize. theV operation of the. rst, motor,

,secolod D. C; tachometer driven by the second meten anadl. means. to. degenerativelyfeed a portinn- Of. the tachometer output tothe second bridge modulator ampl-ier to stabilize.. the `operation of the second motor.

12.. Apparatus comprising. a. reversible driving means responsive to an error voltage, a` variable voltage source. coupled. to said driving. means to provide a. measurement. potential for shifting a measurement, indication inv a. direction to. reduce said. error voltage. to zero..r a Second.. variable voltage. source coupled tcsaid. driving means, to provide a, measurementy rate potential, a second Areversible.y driving. meansy responsive to thev measurernent-ratepotentiaL. and a third variable voltageJ source coupled to.J said, second drivingr means for supplying a potentialy in opposition to the measurement rate potential..y

13.. Apparatus. comprising. a first reversible driving. means; responsive.. to an error voltage,A a Variable. voltage source coupled. to said rst driving means to provide a, measurement potential tor, shitting. a` measurement indication in that direction which will reduce. the error voltage.- to nero.r a. secondvvariable voltage source coupled to said. driving means to` provide a measurement k2 rate2 nctlaltle.1,. a second reversible drinne: means respo:I rsive-A to.. saidimeasurementrate potentiele@ thirst.varia-121e. voltage sourcefcoupled to.. said; `ste-..- ond drivinemcans 15er-j supnlyinaapotentie-.1.1m opposition, toi. the. me csereznent` rate potentiel,

and'. a. slewing. .voltage source.; andv switchfmeans Y for:v disconnection-Said first.- drivina. means fram said error rcl-tasascuree marconi-ine it fascie slewinsvolmgc Scuxcmwhemther apparatueiete bensed-.forislewinar 14., Apparatus. cmu-prisma.I a. rst. reversible driving- Yrmsaris--frcsnonsive to .an error voltage?. a variable. voltage. source. comolcdtos said .rstidrivmamans-tc Dmlfide e *,mesutemeni Intentia! ,for shifting., a measurement. indicatioxtltnat direction Whicni-willereduce theerror rciaSe-to zero, a. sccondj variable. voltages source l coupled t0 Said, drivinameansito provide. a. measurement rate potential.. a.t second rcversiloledrivins means respfmsive. to vsaid measurement, ratepotentien' a Gnd diwivg.; mme @Ii- SllPlY-ng. 14 aY-fpnal opposition to. the measurement-.rate.pctentia1, ano means adapting 'said-f,.,aiparatusi forr-aioedftrack: ing, .said means., cfnnn.risiriiitvr mist- .contrc1.. means tor defenergizinssaid nrstdrivina means. means for ol,isccnnecting.y said third variable voltage source fromsadsecond drivngimeans and means inge. Y

RnrEnnNcas' clrnof Y The following referencesA areonrecordin: the file. of thsrpatent.: Y

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